1. Field of the Invention
The present invention relates to oxygen sensors and, more particularly, is directed toward a method and apparatus involving high speed sensing of oxygen.
2. Description of the Prior Art
A variety of oxygen sensors have been developed to detect and measure the oxygen content of blood samples and physiological gas samples. Typical examples of prior art oxygen sensors are described in U.S. Pat. Nos. 3,223,597, 4,042,465 and 4,085,024 and the references cited therein. One major application for prior art oxygen sensors is in the medical field, for example, in clinical medicine for use in the cardiac catheterization laboratory and cardiac surgery for measurement of oxygen in blood and gases. Another application for oxygen sensors is in the industrial field, for example, in manufacturing processes that require measurement of oxygen such as in the brewing of beer, manufacturing of paint, dyes and the like.
Currently, oxygen cells and sensors that are capable of accurately detecting and measuring oxygen content in a fluid or gas suffer from the disadvantage that they require a relatively long period of time to complete a single measurement. For example, in blood it takes approximately four minutes for a sensor to complete a single measurement. Three minutes are used for sampling and one minute is used to recondition the cell. In certain cardiac catherization procedures, it may be necessary or desirable to measure up to two dozen separate blood samples from various sites in the heart for complete diagnosis. At the measurement rate previously noted, the time required to make these measurements would exceed one hour and thirty minutes. Since catherization procedures involve risk to the patient, they are time critical. The inordinately long period of time that is needed to complete the diagnostic measurements using prior art sensors is outside acceptable medical standards. Although there are oxygen sensing devices that are presently available which are capable of operating at fast sampling rates, these devices suffer from the disadvantage of limited accuracy and the inability to measure gases.